Realistically (pun very much intended with respect to the scanner brand) you're going to end up with something that's utterly useless in most respects if you were to attempt to do what you're hoping to attempt to do, as convoluted as that sounds.
Because most every frequency that hobbyists tend to monitor
in general lies between 100 kHz and
roughly 1 GHz then such a hack on that hardware will eventually prove (again) useless because to
lower the effective frequency reception capabilities of the current stock hardware you'd have to lengthen the receiving element - and by this specific range of frequencies from 100 kHz to 1 GHz I mean all the public service and commercial comms that take place around the world, I don't mean microwave transmissions well above 1 GHz except perhaps the Ham band around 1.2 GHz aka the 23cm band and I personally have never known of anyone that uses that band but it's there for that purpose.
If I were to make a suggestion myself I'd say go for a discone if you have the ability to get one, I won't recommend a particular brand or model since there's a ton of info on such antennas in this very subforum already (the Scanner/Receiver Antennas subforum where this thread is posted). I'm sure someone else will probably say "if he's in the mountains at a high altitude then perhaps a discone isn't a good antenna because of how the discone's reception propagation works - it receives better if the transmitters are
above the discone itself..." and that's true to many degrees, but for an all-around wideband that that can pull in a huge swath of frequencies I'd like to think it's one of the best options out there in any situation.
There are some really good all-band or wideband design antennas that aren't discones, of course, like the popular Scantenna which I believe it no longer in production but you might find one on eBay or from someone here at RR in the Classifieds section for a decent price, or something of a similar nature that could work great in your particular set up there in the mountains. Being up that high is a good thing for reception, really, but if you're in the middle of a large chunk of mountainous area they could also prove to be detrimental to reception by literally blocking signals with billions of tons of rock.
Anyway, some things to consider I suppose, pretty sure others will chime in here quick so, keep an eye on the thread as more info comes in.
I will add one thing, just for the record: the Pro-26 is a very
very old analog scanner and while it's quite capable in the analog reception respect with a very wide reception range, you
might consider thinking about getting something newer for a variety of reasons:
might have some digital systems in your reception area (P25/DMR/etc) as that branch of comms is expanding rapidly over traditional analog systems), newer scanners have vastly improved reception sensitivity and lower noise problems overall, and other reasons as well.
Hell, for $10-25 these days you can buy one of the "cheap USB TV tuners" - literally a USB stick that's a TV tuner designed for the European digital TV standard years ago but was rapidly gutted out and replaced with an entirely different system that was incompatible so a few million of those sticks became useless instantly until some talented coder realized he could modify the driver for the tuner itself and then wham, suddenly it became a wideband radio receiver and sparked a new "boom" in the hobby with RTL-SDR. There's a subforum here about it with a lot more info:
https://forums.radioreference.com/software-defined-radio/
and considering what's possible with even a $10 RTL-SDR based stick for a tuner + something as simple as SDR# (SDRSharp, the most popular SDR application there is) and a working PC/Mac/Linux desktop or laptop (SDR# is a Windows app but it can run on Linux and macOS with virtualization and other tricks, plus those platforms have their own SDR applications as well coded for them specifically) you can tune in pretty much anything from 25 MHz to 1.7 GHz (the higher end is less sensitive on the lower cost RTL-SDR sticks, if you spend more money to get something like an Airspy or SDRplay you get a much better total coverage range, especially with SDRplay which offers 10 kHz to 2 GHz or even higher as I'm not sure about the current spec, think it's like $100 these days, an awesome piece of hardware).
Basically, having that old analog scanner is fine if it's doing exactly what you want but there are other options now that offer a lot more potential, it's up to you of course to decide what your intentions are for the future. Personally I use RTL sticks myself for a few years now, I did have a physical digital capable scanner recently - my first digital one actually, and I sold it fast for a decent profit because I didn't actually need it anymore thanks to SDR and how it has become my go-to way of monitoring with my laptop (I don't do desktops anymore).
Hope something here in this post proves useful.
